Expression of Cathepsin B and Cystatin A in Oral Lichen Planus

Cathepsin B (Cat-B), a cysteine protease, and cystatin A (Cys-A), a protease inhibitor, are involved in the immune response. This study determined Cat-B and Cys-A expression in oral lichen planus (OLP) by immunohistochemistry.

Thirty specimens each of OLP and healthy gingiva (HG) were included. The expression pattern, the number of positive cells, the staining intensity, and the immunoreactive score (IRS) of Cat-B and Cys-A were investigated. The data were analyzed by using unpaired t-test, Chi-square, and Spearman's rank correlation.

The Cat-B expression in OLP was observed as cytoplasmic staining in the epithelial cells, whereas Cys-A expression was exhibited in the nucleus and cytoplasm of the epithelium. An increase in Cat-B staining intensity was also observed in the basal cells. Conversely, the high staining intensity of Cys-A was observed in the stratum spinosum, but not the stratum basale. In HG, Cat-B expression demonstrated a relatively consistent intensity in the epithelial layer. The Cys-A expression in HG was similar to OLP with a lower staining intensity. The mean percentage of positive cells and the IRS score of Cat-B and Cys-A in OLP were significantly higher than HG (P < 0.05). There was no correlation between Cat-B and Cys-A levels in OLP. Interestingly, Cat-B expression in erosive OLP was greater than in non-erosive OLP (P < 0.05).

The Cat-B and Cys-A expression in OLP was more outstanding than in HG, suggesting possible roles for the process of OLP pathogenesis. In addition, Cat-B expression may be an indicator of the disease severity.